THE PLIGHT OF ENDANGERED SPECIES

For every species that is alive today, perhaps a thousand more have lived previously and become extinct. Most of these extinctions occurred before humans evolved, and the species are known to us only through fossils.

Extinctions are a natural part of evolutionary processes, but through most of the history of life on Earth, biological diversity has been increasing.

Periodically, however, major changes in the conditions on Earth have caused the collapse of living systems, and large percentages of species a have become extinct. These species will never return. It takes millions of years for life forms to diversify again.

The current extinction crisis is unique, in that the loss of biodiversity is occurring very rapidly, and the causes of the crisis are the activities of a single species: human beings. Some scientists believe the current crisis began when humans and their domestic animals first began to colonize the various parts of the globe.

Others believe it began around 1600, when human population growth exploded, and the level of per capita resource consumption began to rise dramatically in some parts of the world.

Of the species that are best known, the so-called "higher animals," more than one percent have become extinct in the last 400 years and the overwhelming majority of these extinctions are anthropogenic. Many more species are in danger of becoming extinct if we do not act quickly to conserve them.